Many individuals work in proximity to sources of radiation or ionizing energy. Although some sources emit relatively small doses of ionizing energy, during the course of a career, an individual may receive a cumulative dose of ionizing energy that is dangerous. Prolonged exposure to and/or increased doses of ionizing energy can cause cellular and chromosomal damage, potentially increasing the risk of cancer and other illnesses. As there is no clearly defined safe threshold for ionizing energy exposure, even relatively small doses could be considered dangerous and should be minimized to reduce an individual's lifetime dose of ionizing energy to the minimum amount possible.
Many government agencies, industries, and employers have established protective measures intended to reduce the radiation dose received by individuals who work in proximity to known emitters of ionizing energy. Some examples of these measures include the use of protective garments, personal dosimeters, and proscribed working distances from the emitter. Unfortunately, each of these measures includes deficiencies.
Referring now to FIG. 1A, an example of a known protective garment 104 is illustrated. Protective garments 104 offer imperfect protection from ionizing energy as much of the body of an individual wearing the protective garment 104, such as the individual's arms, neck, and head, may remain unshielded. Other protective garments are available that cover more of an individual's body. However, as will be appreciated, as the size and body coverage of the protective garment increases, the weight of the protective garment also increases. Protective glasses, gloves, and masks are also available but include many of the deficiencies of the protective garment 104.
Protective garments 104 are also generally heavy and burdensome due to the protective materials, such as lead, they incorporate. Some protective garments 104 are known to weigh at least 10-15 pounds. Certain individuals who work in proximity to emitters of ionizing energy, such as surgeons and operating room staff, may be required to wear protective garments 104 for many hours. For example, some surgical procedures that are performed in conjunction with periodic use of ionizing energy may last from 6-10 hours or more. The prolonged wear of protective garments 104 can accelerate mental and physical fatigue because of the weight and discomfort of the garments. Unfortunately, this can lead to mistakes. Frequent wear of heavy protective garments 104 can also result in repetitive stress injuries to the individual.
Referring now to FIG. 1B, some protective garments 108, or drapes, are known which are suspended from a ceiling or from an emitter 112 of ionizing energy, such as a fluoroscope. These protective garments 108 may detrimentally limit the mobility of the individual. Additionally, individual's using such protective garments 104, 108 may experience decreased dexterity. Generally, as the size and body coverage of protective garments increases, the mobility and dexterity of the wearer decreases. The individual may require increased effort to move their arms and hands due to the weight of the protective garments 104, 108. This problem is exasperated when the protective garments 104, 108 extend over the arms of the individual. Further, some movements of the individual's arms may be restricted, or are not possible, when wearing one of the protective garments 104, 108. Although this may not be a problem for some individuals or in certain situations, individuals performing delicate work, such as a medical procedure, may not be able to adequately perform work while wearing one of the protective garments 104, 108. In a surgical setting, freestanding protective garments 108 can also lead to breaks in sterile technique and contamination of surgical sites. In addition, the weight of the garment is such that continued use by an individual can be tiring, and sometimes prohibit prolonged use due to fatigue.
Another less apparent problem with protective garments 104, 108 is that the protective layers within the protective garments 104, 108, such as lead, lose effectiveness over time. More specifically, the protective layers can break down due to stress caused by movement and flexion of the protective garments 104, 108. It is generally impossible for individual's wearing the protective garments to visually determine if the protective layers are defective or degraded. Because of this, some individuals may unwittingly be exposed to ionizing energy while wearing a defective or degraded protective garment 104, 108. Ensuring protective garments 104, 108 are functional requires periodic inspection, maintenance, and replacement of the protective garments 104, 108. As will be appreciated, proper inspection and maintenance of protective garments 104, 108 increases the time and expense associated with their use.
Unfortunately, many individuals that work in proximity to emitters of ionizing energy, including surgeons and operating room technicians, choose not to wear protective garments 104, 108 because of these and other problems associated with their use. As will be appreciated, protective garments 104, 108 provide no protection if they are not worn or when they are worn improperly.
Some protective measures direct or encourage individuals working in proximity to emitters of ionizing energy to wear or carry personal dosimeters. Many different types of personal dosimeters are known. However, as will be appreciated by one of skill in the art, dosimeters do not protect an individual from ionizing energy. Further, many dosimeters do not provide the individual with immediate information regarding doses received. For example, very few dosimeters provide immediate warnings to individuals when doses exceed a preset amount.
Dosimeters also do not necessarily detect the highest dose of ionizing energy received by an individual. This is because dosimeters only record the dose of ionizing energy received by the dosimeter at the location where the dosimeter is worn or carried by the individual. As many emitters produce ionizing energy that is highly focused, such as into a beam 216, doses received by different parts of an individual's body may vary greatly. More specifically, as illustrated in FIGS. 2A-2D, amounts of ionizing energy 204 measured in zones 208A-208F proximate to an emitter 112 vary based on distance and orientation of the emitter 112. Accordingly, the dose received by parts of an individual's body 214 may be higher than the dose recorded by a dosimeter. example, in 2A the individual's hands are receiving a larger dose of ionizing energy than other parts of the individual's body. Thus, a dosimeter worn on the individual's torso may record lower doses of ionizing energy than received by other parts of the individual's body 214. Because of this, even if a dosimeter is capable of providing a warning to an individual when a dose of ionizing energy exceeds a threshold, the dosimeter may not provide a warning when expected as the dosimeter may not receive and record the highest dose of ionizing energy received by the individual.
Another deficiency of some dosimeters is that they require batteries. Other dosimeters must be activated to record doses of ionizing energy received. Individuals using dosimeters with discharged batteries, or who forget to activate their dosimeter, may receive unrecorded doses of ionizing energy. An additional problem occurs when an individual forgets to wear or carry the dosimeter.
Another way to protect individuals working around emitters of ionizing energy is by proscribing working distances from the beam of ionizing energy produced by the emitter. One article reports that at a distance of 2 meters, exposure is reduced to 0.025 percent of the intensity of the direct beam. See Chris Moore et. al., Reducing Radiation Risk in Orthopaedic Trauma Surgery, Bone & Joint Science, Vol. 2, No. 7, July 2011, available at: http://www.smith-nephew.com/global/assets/pdf/products/surgical/trigen_sureshot_reducing_radiation_risk_wp_lores.pdf (last visited Jun. 7, 2016) which is incorporated by reference herein in its entirety. This separation distance may be a good general distance, but it is only useful if individuals are aware of the location and path or pattern of the beam of ionizing energy.
Referring again to FIGS. 2A-2D, a beam 216 of ionizing energy produced by an emitter 112 may have a variety of paths based on the orientation of the emitter 112. Further, although the beam produces the highest possible dose, another source of ionizing energy is scattered ionizing energy which is produced by interaction between the beam 216 and anything the beam strikes, including people, tables, instruments, equipment, walls, and floors. It is difficult for individuals to predict the pattern of scattered ionizing energy produced during a shot of an emitter 112 as the pattern of the scattered ionizing energy varies based on objects the beam strikes. The pattern of the scattered ionizing energy also changes as the orientation of the beam changes. Because of the variation of the shape of the pattern of scattered ionizing energy, it is difficult for individuals to decide where to stand to receive a minimal dose of ionizing energy.
In one example, the scatter pattern from a C-arm fluoroscope, such as the emitter 112 illustrated in FIG. 2, is not a standard sphere with a uniform radius. Further, and referring now to FIG. 2E, zones 208 with higher amounts of ionizing energy may extend a greater distance from the target 220 on a first side of the target that is proximate to the emitter 112 compared to a second side of the target that is distal to the emitter 112. More specifically, as illustrated in FIG. 2E, an individual 214A on a first side of the target 220 proximate to the emitter 112 is mostly in the highest two zones 208A, 208B. A second individual 214B on a second side of the target 220 is standing predominately outside of zone 208A and will receive a lower dose of ionizing energy from the emitter 112. However, both individuals 214A, 214B are in similar positions of less than about 1 meter from the target 220.
Another problem is that the pattern of scattered ionizing energy can also change from one source 112 to another source. The pattern will also change based on the power setting and focus of a particular emission of ionizing energy produced by the source 112, the orientation of the source 112, and the proximity of the source 112 to a target 220, such as a patient. Accordingly, individuals may move the proscribed distance from the source 112 and/or the beam 216 yet still not be far enough away to be safe in which case the individuals will receive an accidental, and unnecessary, dose of ionizing energy. Thus, merely proscribing a distance to separate individuals from a source of ionizing energy may not adequately protect them from scattered ionizing energy.
Another deficiency with proscribing a separation distance is that some individuals may move further than necessary based on the direction of the beam or the pattern of the scattered ionizing energy. For example, referring to FIG. 2C, although the individual 214 is relatively close to both the source of ionizing energy 112 and the beam 216, the individual predominately outside of zones 208A-208F and is receiving a very small dose of ionizing energy. Thus, it may not be necessary, or beneficial, to direct the individual move further away from emitter 112.
Additionally, the separation distance can lead to inefficiencies and other problems. Referring again to FIG. 2C, if individual 214 is performing a task, moving further away from the source 112 or beam 216 when not necessary may waste time. In some situations, such as during surgical procedures, when a doctor 214 moves further away from the patient 220 than necessary, the length of the surgical procedure may increase, increasing risks fur the patient. Some of the risks are those associated with excessive anesthesia or blood loss. Moving an excessive distance from the patient 220 may also increase the risk of the doctor 214 becoming contaminated. The further away a doctor or other medical processional moves away from the sterile field, the higher the likelihood of becoming contaminated. This is because with increased distance from the surgical field, the doctor 214 is more likely to touch a non-sterile surface or move outside of a clean, laminar airflow within the operating room.
Accordingly, there is a need for a system and method that can detect the presence of an individual within a predetermined proximity of an emitter of ionizing energy.